Frequently asked questions

Below you can read through frequently asked questions. For additional information refer also to the Measurement page and use tooltips when entering values in the calculator itself.

For what spokes can I use this calculator?

Regarding spoke type, this calculator will accept both regular J-bend as well as straight pull spokes. Make sure you use standard metal or stainless steel spokes. This calculator is not intended to be used for titanium spokes as they tend to deform more when tensioned.

How accurate is the spoke length calculation?

Probably more than you would need it anyways. That said, calculation output is limited to two decimal points. However, you will probably need to round the spoke up or down to integer. Read more to see advice on this topic.

What are consequences of having inappropriate spoke length in real world?

Spoke length that is either too long or too short will be problematic. Being too long, and the spokes protrude past the end of the nipple. Such spoke position can poke a hole first in the rim strip and eventually damage the inner tube. Too long may also mean you run out of spoke threads as you attempt to tighten that spoke further. This will greatly influence the tension you are after and you will be unable to get spokes tight enough.

On the other hand too short means that spoke won’t extend into the head of the nipple. So there will be inadequate thread engagement and this can eventually lead to thread failure or the spokes loosening. This will become your wheelset’s weak point where spokes might break but more importantly when using more fragile alloy nipples, they can easily crack when spoke is not threaded to the end to support them in the rim bed.

What units do I need to use in this spoke calculator?

Spoke lengths are given in millimeters, so please use millimetres (mm) for defining sizes. Only the max recommended tension, which is the optional input needs a kgF unit when being filled out. You can enter decimal values if you desire. Please make sure to fill all the inputs and note that you are supposed to enter only bare numbers without any units.

I don’t have all the dimensions about my hub or rim.

You should take a look at my Articles page, where you can learn more on how to properly measure your hub if you have partial specs about it or none at all.

Does having different nipples affect total spoke length?

Depends, but more likely than not the answer would be yes. Many times you don’t have to adjust calculation for different nipples (especially when switching between 12 and 14mm nipples) since generally they are not threaded longer or shorter. Usually 16mm long nipples are longer in total (only barrel is larger) to accommodate for thick carbon rim beds, but they have the same amount of threads.

However, some nipples - DT Swiss in particular - are known to be threaded shorter for small sizes and longer for bigger sizes (16mm). In their calculator, you will see the calculated spoke length for 16mm nipple at least 2mm shorter than if 12mm nipple is being used.

So, what do I do? Like Damon Rinard once stated - the basic question remains the same: at what diameter do you want your spokes to end? That is what you enter for ERD. If you have specific nipples for the job, make sure to make your wheel's ERD measurement check with those exact nipples.

Should I therefore measure the ERD of the rim myself?

If possible, having the rim at hand and nipples, that will be part of your final setup, I would definitely answer, yes. Even established rim producers like DT Swiss warn about different rim’s ERD measurement technics that could affect your final calculation.

Should I round the spoke length up or down?

Despite getting spoke length accuracy up to two decimals in the calculator, most of times you will have to make a compromise by rounding it up or down. Some spokes are available only in odd, some in even sizes, with 2mm increments between different sizes. Usually you round down the length calculated as you don’t want spokes to poke outside nipples or to run out of threads on spokes when assembling the wheel.

To know exactly what you will be facing if it comes to rounding up or down, measure the the ERD yourself and see what happens if you choose a longer spoke. Try to wind up the spoke a few more turns and see if the nipple will allow it. Some nipples in combination with your particular spoke will cause your spoke stuck when just a millimeter past an ideal length. That means you have run out of threads on your spoke.

What rims can I use with this calculator?

As long as you have the right ERD, it really doesn’t matter. You can use it on standard alloy rims, rims with eyelets, modern carbon rims with thick rim beds or even asymmetric rims. This topic is discussed in the next faq accordion.

How do I use this calculator when having asymmetric rims?

You only need to enter the OSB value, that stands for spoke offset bed. This means how far spoke holes in your rim are closer to one side of the rim (off-center). You absolutely don’t need to adjust flange to center or any other variable.

Very important: please keep track of which wheel you are actually calculating. For the asymmetric wheels, calculation algorithm differs between front and rear wheel.

I see there is also a tension input available, what does it mean?

This is the only input that is of optional nature. Carbon rims in particular have a maximum spoke tension stated on them which should not be exceeded. You should expect numbers somewhere in a ballpark of 120KgF to 180kgF (~1200N-1800N). Try not to confuse it with spoke’s maximum tensile strength which can easily exceed 3,000N. Spokes can easily withhold the tension you will put on them, however, when you exceed max tension for the rim, it will most likely crack near nipple holes. Also, it has been proved that putting more tension on the wheel doesn’t affect its stiffness unless spokes on one side are fairly slack.

So, calculators max recommended tension feature only offers calculation regarding on your maximum input value. Taking in consideration that your rim’s max tension is for example 130KgF, the side with smaller bracing angle (more vertical) which is usually drive side, can be tensioned close to its maximum. But what about the non-drive side? If hub isn’t symmetrical, tension values for left and right shouldn’t be equal, right? Based on tension ratio (%), this calculator will calculate how much pressure you can put on the other side as well.

You can then use this figure to compare different hubs or even try the same calculation with an asymmetric rim and see how it affects tension ratio of the wheel.

I don’t have a maximum tension specification about my rim.

No problem, don’t use this input as it is the only one, that is optional. Just leave it blank. However, when it is available, this spoke calculator can tell you much about tensioning and dishing details of your setup.

I want to explore all the advanced options, this calculator offers.

Great! You are becoming a proper wheelbuilder. Once you enter dimensions and press the CALCULATE button, besides spoke length the calculator will reveal a graph icon. Once you click on it, you will be able to look at your wheelset input data, spoke length, tension ratio (in % and also recommended KgF for each side) and bracing angles. In that way you will be able to keep a record about your setup and also for comparing different component’s effect on your calculation. Give it a try!

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